As an example, I found $166 roundtrip flights departing Raleigh RDU on Thursday, December 6, returning from Cancun CUN on Thursday, December 13.

Travel is valid through February 13, 2019, with a 7-day advance purchase required. Avoid blackout dates on November 17-26, December 20, 2018 - January 8, 2019, and January 18-21, 2019. Some routes are seasonal and most routes are only operated on select days each week. Click on the fare details for more information on each route.

Keep in mind that Frontier charges extra for any bag larger than a small personal item (small backpack, purse, etc.). Pack a swimsuit and hit the beach. If you need to bring more, checked bags start at $25 each way. Larger carry-on bags start at $30 each way.

Another option is to add the Works bundle when booking on FlyFrontier.com, which includes one checked bag, one standard sized carry-on bag, stretch seating, no change fees, and refundability. Adding the Works to my example from Raleigh to Cancun brings the fare to $325 roundtrip.